This invention generally relates to dynamic load/unload technology in magnetic disk drive assemblies and, more particularly, to a combination of load/unload ramps with shipping combs and/or limiters, such as disk, tab, flexure, suspension or arm limiters.
Disk drive memory systems store digital information on magnetic disks, which typically are divided into concentric tracks, each of which are in turn divided into a number of sectors. The disks are rotatably mounted on a spindle and information is accessed by read/write head assemblies mounted on pivoting suspension arms able to move radially over the surface of the disks. The radial movement of the head assemblies allows different tracks to be accessed from the inside diameter to the outside diameter of the disks. Rotation of the disks allows the read/write heads to access different sectors of each track.
In general, head assemblies are part of an actuator assembly, which also typically includes a suspension assembly, a flexure member and an arm, among other things. Head assemblies typically include a magnetic transducer to write data onto a disk and/or read data previously stored on a disk. Head assemblies also typically include a body or slider having an air bearing surface which, in part, functions during operation to position the magnetic transducer a specified distance from the surface of the spinning disk. In general, it is advantageous to position the magnetic transducer as close as possible to the disk.
A primary goal of disk drive assemblies is to provide maximum recording density on the disk. A related goal is to increase reading efficiency or to reduce reading errors, while increasing recording density. Reducing the distance between the magnetic transducer and the recording medium of the disk generally advances both of those goals. Indeed, from a recording standpoint, the slider is ideally maintained in direct contact with the recording medium (the disk) to position the magnetic transducer as close to the magnetized portion of the disk as possible. However, since the disk rotates many thousands of revolutions per minute or more, continuous direct contact between the slider and the recording medium can cause unacceptable wear on these components. Excessive wear on the recording medium can result in the loss of data, among other things. Excessive wear on the slider can result in contact between the magnetic transducer and recording medium resulting in failure of the magnetic transducer or catastrophic failure.
Similar to recording, the efficiency of reading data from a disk increases as the read element is moved closer to the disk. Because the signal to noise ratio increases with decreasing distance between the magnetic transducer and the disk, moving the magnetic transducer closer to the disk increases reading efficiency. As such, magneto-resistive heads in current disk drives typically operate at an average spacing from the disk surface of approximately 20 nanometers to up to approximately 50 nanometers. This range of spacing is required due to several reasons, including manufacturing tolerances of the components, texturing of the disk surface and environmental conditions, such as altitude and temperature. These factors, and others, result in variances in the spacing between the magnetic transducer and the disk, which can cause the magnetic head to fly too low and contact the spinning disk.
The dynamics of an operating magnetic disk drive assembly require a study and understanding of the interaction between the head assembly and the disk. In general, the study of the design, friction, wear and lubrication of interacting surfaces in relative motion is referred to as tribology. Also, the term head stack assembly generally refers to the head assembly, the suspension and the e-block.
In typical applications, when power to the disk drive is turned off, the suspension arm moves to the inner diameter of the disk and directs the head assembly to land on a specified area of the disk, commonly referred to as the Laser Texture Zone, located at the extreme inner diameter of the disk. At rest, the head assembly rests on the surface of the disk in the Laser Texture Zone. When power is turned back on, the disk starts to spin, generating a body of moving air above the disk that lifts the head assembly above the surface of the disk. The head assembly then is moved to the desired location relative to, and above, the spinning disk.
The Laser Texture Zone is designed to provide sufficient length and breadth to accommodate the landing of the head assembly onto the disk during power off, and to accommodate the lifting of the head assembly off of the disk during power on. The Laser Texture Zone obtains its name from bumps created by a laser that results in a rough surface to reduce stiction of the recording head when resting on the disk. Because of the interaction between the head assembly and disk, including the forces imparted during start and stop operations and the direct contact during power off, the Laser Texture Zone typically is not intended to store information.
Optimally, the head assembly contacts the disk only within the Laser Texture Zone. The remainder of the disk, other than the Laser Texture Zone, is designed to optimize the recording, storing and retrieving of information. This remainder of the disk, referred to as the Data Zone, extends outwards to the outside diameter of a typical disk. To protect the disk from impact forces and stiction forces from the head assembly, among other things, the base magnetic layer of a disk typically is covered with a protective layer of carbon overcoat and an outer layer of lubricant.
A more recent development in head-disk assembly tribology is dynamic load/unload technology. Rather than designing the head assembly to land on, rest on and lift off of the surface of the disk in the Laser Texture Zone, dynamic load/unload technology suspends the head assembly on a ramp, typically located in proximity to or outside of the outside diameter of the disk, although it may be located at any fixed radius. More specifically, a ramp is built into the housing of the magnetic disk drive assembly overhanging the outer most portion of the disk or adjacent the outside diameter of the disk. A tab or an extension of the suspension arm rests on the ramp, thereby suspending the head assembly, either above the disk or just beyond the outside diameter of the disk. Even at rest, the head assembly is designed to not be in direct contact with any part of the disk. When the power is turned on and after the disk is spinning, the head assembly is designed to move down the ramp and fly above the spinning disk.
In a conventional disk drive using contact start/stop technology, the head assemblies typically are manufactured and then transported to another location for assembly into the disk drive. To protect the head assemblies during transport, a shipping comb typically is utilized, which holds apart the opposing head assemblies and protects the entire assembly. Such a conventional shipping comb is made of relatively inexpensive plastic and is discarded after use.
To assemble head assemblies into a conventional disk drive using contact start/stop technology, the shipping comb typically is replaced with a merge tool (also called a process comb), which holds apart the opposing head assemblies, among other things. The merge tool also positions each head assembly over, and lowers each head assembly onto, the slowly spinning disk. This process, commonly referred to as merging, places each head assembly onto the surface of the disk, typically on a portion of the outer diameter. The merge tool then is swung outwardly and removed, and the head assemblies move to a parked position, typically on an inner portion of each disk. Due to the complex nature of the process, there is a possibility of yield loss during assembly, e.g., dinging disks, bending suspensions, etc. Dynamic load/unload technology facilitates the merging process by providing a surface on which to park the tabs of the suspension arms. A merge tool is no longer needed to spread the head assemblies during assembly.
However, even when dynamic load/unload technology is used, a shipping comb is still needed to protect the head assembly during shipping, storage and handling prior to assembly into the disk drive. Of particular importance is the protection of the distal end of the head assemblies, where there are fragile connections and other components. For example, a shipping comb advantageously includes protection for sliders and flexures, particularly as those components become smaller and more susceptible to damage. However, as the head assembly and its components become smaller, it becomes increasingly difficult to maintain sufficient room for such protection. For example, as the head assembly becomes smaller, the merge tool has less area on which to hold onto, leaving little or no room for a shipping comb. One solution is simply to eliminate the part of the shipping comb that provides head assembly protection. Also, as suspensions become shorter, there is less space for a shipping comb to be attached to the suspension between the suspension bending radius and the slider, particularly without damaging it.
One existing solution to this problem is to not touch the load beam between the slider and the swage point, but rather to use a center tab at the end of the suspension for merging purposes. Tabs on existing dynamic load/unload ramps are generally too short for the merging tool and ramp to coexist. This center tab would be the same tab for dynamic load/unload, although there is a compromise between the design objectives of merging, which requires a relatively longer tab, and of dynamic load/unload, which requires a relatively shorter tab.
A significant advantage of dynamic load/unload technology is the reduction of xe2x80x9chead slap,xe2x80x9d the sudden impact of the head assembly onto the disk during non-operational shock. This advantage is achieved by parking the arm of the head assembly off the outside diameter of the disk and by providing a ramp for takeoff and landing. However, dynamic load/unload technology often does not prevent other impacts between the disk and head stack assembly, e.g., arm to disk contact.
It is advantageous to park the arm close to the disk to reduce inertia and seek times, and to reduce come-ready time. To minimize seek times, the arm is typically parked overlapping at least a portion of the outside diameter of the disk. This positioning of the arm creates the possibility of undesirable contact between the arm/swage plate and the disk. As a result, arm limiters and/or suspension limiters may be necessary to protect both the head assembly and the disk. Even if the arm is parked off of the outside diameter of the disk, it may be necessary to limit suspension motion. Suspension motion during shock can cause excessive flexure motion, resulting in deformation of the flexure, which negatively affects pitch and roll, static attitude and ultimately proper flying of the heads. However, installing such limiters in the head assembly as an extra part is difficult technically and expensive in view of current assembly cost and time requirements.
A standard industry test of disk drive assemblies, referred to as a tilt drop test, creates relatively short shocks of approximately one third of a millisecond. In the absence of arm and suspension limiters, a typical disk drive assembly may not pass these tests. If such limiters are necessary, they are an extra piece of equipment, typically an extra screw, and must be installed after the arm, increasing material cost, assembly time and assembly complexity. Installing an additional piece also will result in yield loss, by damaging some drives during the assembly process.
As such, a need exists for providing head assembly protection in a magnetic disk drive assembly incorporating dynamic load/unload ramp technology, as well as providing motion limiters for various components.
This invention generally relates to dynamic load/unload technology in magnetic disk drive assemblies and, more particularly, to combining load/unload ramps with shipping combs and/or limiters, such as disk, tab, flexure, suspension or arm limiters.
In one embodiment of the invention, a unitary ramp comprises an in drive ramp for each head assembly in a disk drive assembly, a shipping comb to protect the head assembly during shipping prior to assembly into the disk drive assembly and to aid an assembly and one or more limiters to restrict the movement of various components of the head assembly prior to after such assembly. Unlike conventional shipping combs, the unitary ramp of the present invention is not removed and discarded during assembly of the disk drive assembly.
Further, the unitary ramp may include a limiter for one or more of the arms, tabs, flexures and/or suspensions of the disk drive assembly. Such a limiter limits the movement of and provides protection for the designated component, during shipping, prior to and during assembly into the disk drive assembly, and thereafter.